Any worker who lifts and carries objects—such as packages for delivery, construction materials, manufactured goods, or patients—is at risk of musculoskeletal injury. Various methodologies exist that analyze lifting tasks to quantify musculoskeletal risks, such as the National Institute for Occupational Safety and Health (NIOSH) method. One system for applying the NIOSH equation is described in U.S. Pat. No. 5,621,667. This patent describes an instrumented analysis system based on a retractable cable and potentiometer system which can determine the NIOSH equation multipliers indicative of physical parameters related to a lifting task under analysis. However, the system is difficult to implement in a normal working environment since it requires a dedicated space to set up the instrumentation and experienced personnel to operate the system. As such, the system of the '667 Patent is more suited to a laboratory environment than a regular work environment.
Published U.S. Patent Application No. 2007/0250286 describes a motion analysis system that can be used to alert a worker that their current motion is not optimal, upon detection of a specified criterion being exceeded during a performed task. Such a criterion can be calculated by applying common work place safety assessment tools, such as the NIOSH equation, or other similar measures previously mentioned using the collected data. Sensor elements attached to movable body segments record movement parameters including angular velocity and acceleration. A control device receives the movement parameters and determines an overall motion of the movable body segments. The overall motion is analyzed against an acceptable motion model to determine whether the overall motion is within acceptable limits. The sensor elements and control device are lightweight and can be worn during normal movement activities, thereby allowing monitoring of work-based activities, such as lifting or typing.
While it is claimed that the system described in the '286 Application can be used in a number of applications previously relegated to laboratory spaces and dedicated laboratory equipment, the system and method have various shortcomings. As one example, the alarm system is limited and could benefit from other modalities, including wireless transmissions. Further, a more appropriate application of gyroscopes and accelerometers could be deployed to measure body vibrations, spine angle, body posture sway and instability.
U.S. Pat. No. 8,149,126 relates to a system for monitoring the behavior of a subject to detect an incidence of unsafe lifting strategy use or high-risk movement. The system includes a wearable trunk sensor, a wearable thigh sensor, and a portable computing device. The computing device may receive the data from the trunk sensor and/or the thigh sensor via a wireless transceiver. Based on the received data, the computing device determines trunk angle and a thigh angles using a combination of accelerometer and gyroscope data received from the trunk and thigh sensors. Trunk rotation is determined by comparing rotation data obtained from the trunk sensor with data obtained from the thigh sensor. The trunk angle, thigh angle, and/or trunk rotation values are used to calculate a risk level associated with the subject's movement. The system may include additional sensors, such as a weight sensor, to determine the weight of an object being lifted, for example for inclusion in the risk level assessment algorithm. The weight sensors may be shoe borne pressure sensors or pressure sensors mounted into surfaces upon which the subject stands, e.g., a floor, ramp, platform, or truck bed. While the system described in the '126 patent may be useful in some circumstances, the assessments do not take into account hand or arm movements, vibration, or other more sophisticated modalities or computations.